This invention relates to heat sensitive recording material, and more specifically to such material which may selectively conceal an image until subsequent development.
Heat sensitive recording materials are well known in the art and are fully described in patent and other technical literature. Generally, these materials consist of a support (e.g., paper) having a light or colorless color developing layer formed thereon. The color developing layer comprises one or a mixture of color forming materials, such as leuco dyes, and a developer material, such as an acidic substance, which react together upon the application of heat to produce a dark or black image in a selected area. These heat sensitive recording materials are widely used in facsimile and other printing technology where an image is generated by heating selected areas of the recording material with, for example, a thermal printhead, to generate images.
In facsimile technology a transmitting facsimile apparatus communicates via telecommunication lines with a receiving facsimile apparatus, instructing the receiving apparatus to print text and/or graphic information. Generally, a sheet of text and/or graphic information to be transmitted to a remote location is fed into a transmitting facsimile apparatus where the information it bears is converted to an electronic signal and is transmitted to a desired receiving facsimile. The electronic signal instructs a thermal printhead of the receiving facsimile to be activated and to contact the heat sensitive recording material of the receiving apparatus in a pattern which will produce an image corresponding identically to that on the original sheet fed into the transmitting apparatus.
This technology is now widely used due to its tremendous convenience. However, because this technology conveniently prints transmitted text and/or graphic information in its entirety, one drawback of this technology is the inability to retain the confidentiality of sensitive information at the receiving station. Accordingly, there is a need for heat sensitive recording material which will enable facsimile messages to be concealed selectively to persons other than authorized recipients.
It is thus an object of the invention to provide a heat sensitive recording material capable of maintaining the confidentiality of sensitive electronically-transmitted messages. Another object of the invention is to provide a heat sensitive recording material which bears a visible image as well as a latent image which may be developed subsequently by an authorized recipient. A further object of the invention is to provide a heat sensitive recording material able to be processed with a lower energy input. Other objects of the invention will be apparent from the descriptions, drawings and claims which follow.